V$DBLINK

Columns
   ___________________________
 
   DB_LINK
   OWNER_ID
   LOGGED_ON
   HETEROGENEOUS
   PROTOCOL
   OPEN_CURSORS
   IN_TRANSACTION
   UPDATE_SENT
   COMMIT_POINT_STRENGTH

Related:

V$DATABASE 
V$DATAFILE 
V$DBFILE 
V$DB_PIPES 
V$OPTION